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IMPORTANCE OF FAST MEASUREMENTS OF SOLAR WIND PARAMETERS AT THE IP SHOCK FRONT

IMPORTANCE OF FAST MEASUREMENTS OF SOLAR WIND PARAMETERS AT THE IP SHOCK FRONT. Z. Němeček , J. Šafránková , L . P ř ech, O. Goncharov, A. Komárek Charles University, Prague, Czech Republic G. N. Zastenker S pace R esearch Institute, RAS, Moscow, Russia.

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IMPORTANCE OF FAST MEASUREMENTS OF SOLAR WIND PARAMETERS AT THE IP SHOCK FRONT

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  1. IMPORTANCE OF FAST MEASUREMENTS OF SOLAR WIND PARAMETERS AT THE IP SHOCK FRONT Z. Němeček, J. Šafránková, L. Přech, O. Goncharov, A. Komárek Charles University, Prague, Czech Republic G. N. Zastenker Space Research Institute, RAS, Moscow, Russia Moscow, February 6-10, 2012

  2. Outline • Brief description of the BMSW device • A new solution of plasma parameter determination – discussion of (dis)advantages • Examples of measurements • Comparison with measurements of another spacecraft • Importance of fast measurements • Conclusion

  3. BMSW in course of time • Solar wind parameters: density, velocity, • and temperature – with a time resolution of 1-0.03 s • Engineering model - 2005 • Flight model – 2008 • Flight spare model – 2009 • Launch – July 18, 2011 BMSW – engineering model B BMSW in vacuum chamber BMSW – flight model BMSW on the platform

  4. BMSW - principles 6 FCs and each FC is equipped with four grids: grounded grids cover the windows in both diaphragms; a positive control grid is placed between outer and inner diaphragms; and a suppressor grid lies between the inner diaphragm and a collector. Characteristics for different velocities Solar wind bulk energy of 1 keV FC characteristics with homogeneous electric field Influence of finite FC dimensions Influence of finite grid spacing The dependences of the normalized collector current on the spacing between wires Configuration of the electric field in the space between two control grids Safrankova et al. (2008)

  5. BMSW modes • BMSW can measure in two working modes: • Sweeping mode – ion distribution between 100-3 000 eV; time resolution 0.5 or 1 s • Adaptive mode – only 3 points on the distribution; time resolution 31 ms

  6. Energetic section BMSW – Block Scheme HV HV Angular section Current outputs Control unit HV Voltage outputs Mode switching

  7. Example of first measurements Aug 12, 2011 Protons Alphas • BMSW in the sweeping mode; speed of measurements – 0.031 s • a full set of solar wind parameters – 1 s • 3 directed FCs show a change of the speed and density • 3 declined FCs show a change of the solar wind direction • Details of distributions – protons and alphas

  8. Data rate and data compression Steps on the HV voltage are a result of compression algorithm • A full time resolution – 0.031 s – can be transmitted only for rather limited time intervals, a compression algorithm is needed • data from 3 direct FCs are averaged (12 points) in adaptive mode • steep slopes are transmitted with a full resolution and the rest of the sweep is averaged in sweeping mode • 12-point averages are transmitted from 3 declined FCs

  9. Spectr-R ACE Wind Comparison – BMSW, Wind, ACE Spectr-R, ACE, Wind A first comparison of joint measurements of three solar wind spacecraft on August 14, 2011

  10. Interplanetary shock September 9, 2011 Interplanetary shock on September 9, 2011 was observed by SOHO, Wind, ACE and also by Spektr-R BMSW in sweeping mode and compressed data Changes of the density and velocity direction

  11. Comparison of BMSW and WindSeptember 9, 2011 - cont BMSW Wind Is this overshoot real? Moscow time IP shock on September 9, 2011 –preliminary computed parameters with a time resolution of 1 s Still 3 times better than earlier

  12. Why the fast measurements are needed? Changes of the density and velocity direction as short as 0.3 s ? Active experiment in the solar wind?

  13. Why the fast measurements are needed? • IP shock is usually considered as a rectangular step • First measurements of the plasma parameters with 30 Hz time resolution • Oscillations of the flow direction with a period of about 0.3 s • Such oscillations could not be observed earlier, the best time resolution prior to BMSW was 3 s • Detailed analysis impossible due to lack of magnetic field measurements

  14. Plasma waves connected with the IP shock front • A detail of observations • The flow angle can be determined with the full resolution but the resolution of plasma moments is 3 s only • The upstream oscillations are linearly polarized • On the other hand, a clear circular polarization was observed in the downstream region • Further analysis requires magnetic field data

  15. Comparison with WIND magnetic field • WIND magnetic field, 92 ms time resolution • HF waves upstream • Two types of oscillations downstream • The upstream oscillations are circularly polarized • Downstream LF waves exhibit a circular polarization • Polarization of the HF part of downstream waves is not clear

  16. Adaptive mode – compressed data An example of processing of the adaptive working mode. Data compression not only decreases time resolution but it introduces artificial noise

  17. Full time resolution without compression • our data reveal the real fine structure of the solar wind flow • a weak IP shock that cannot be resolved with 1-minute resolution • frequency spectra of density, speed, and temperature are different 20 minutes 30 seconds Comparison with standard data, the same time interval

  18. Data distribution • Web page of the device - under construction • Daily (6 hours) plots of FC currents - ready • Preliminary processed plasma moments with the time resolution of 30 s (density, velocity, and temperature) – under preparation • Detailed data from a short time interval – on the request

  19. Future plans • Finishing of the data processing software • Determination of temporal evolution of photocurrents • Gathering of interesting intervals with full time resolution • Investigation of fast disturbances Thank you • Investigation of solar wind turbulence at kinetic scales • Preparation of a new generation of the BMSW device for future missions for your attention

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